1. Field of the Invention:
This invention relates to electrophotographic copying apparatuses such as copying machines, laser printers, and the like.
2. Description of the Prior Art:
When electrophotographic copying apparatuses such as copying machines are used for a long period of time, the photosensitive drum must be replaced, the developer must be added or replaced, the charging wires must be cleaned or replaced, the used toner must be replaced, and other such maintenance tasks must be done. Generally, these kinds of maintenance tasks take place during servicing or the like, but with the recent spread of the use of miniature copying machines, etc., some copying machines are being made in which a plurality of parts that are essential to form an image are incorporated into the body of the copying machines as a unit, and this unit can be removed from and replaced into the body of the copying machines, making it easy for the user to replace these parts.
In miniaturized copying machines mentioned above, as the optical means that conveys the image of light from the manuscript to the photosensitive drum, there is used a light-transmitting device through which light is converged (trade name, Selfoc lens), etc. This light-transmitting device is constructed so that it usually has a fixed magnification, so when the magnification of images to be obtained is to be changed, the light-transmitting device is replaced with another one with a different magnification.
However, as described above, when electrophotographic copying apparatuses such as copying machines and the like are constructed so as to have an image-forming unit and an optical means that can be installed into and removed from the body of the electrophotographic copying apparatus, the relative positions of the three parts, the body of electrophotographic copying apparatus, the image-forming unit, and the optical means, can readily shift, and when this occurs, the image that is formed is affected for the worse in terms of changes in the magnification, distortion of the image, and the like.
Japanese Laid-Open Patent Publication 58-139162 discloses a copying machine that comprises an optical means fixed to the body of the copying machine and a process kit. The position of the process kit is accurately decided with respect to the optical means by a positioning mechanism. In this way, because the said optical means is fixed to the body of the copying machine and cannot be replaced by another one with a different magnification, it is impossible for this copying machine to form images with a different magnification. Even though the said optical means were constructed to be removably incorporated into the body of the copying machine, because the process kit is mounted onto the said optical means, the said optical means cannot be replaced by another one without the removal of the process kit from the said optical means at the time when changes in the magnification of images are required.